Perimeter protection systems are designed to detect events where intruders approach and/or enter a secure region, using a sensor enabled physical boundary, and to alert security personnel. The traditional security barrier uses a chain-link fence with motion detectors that are tuned to detect the presence of an intruder within a few feet of the fence, along with a security camera that can be directed by the security staff to view the cause of any motion alert. Alternatives to this configuration include the use of infrared beam-break sensors in locations where a physical barrier is not practical, and the use of centralized ground radar systems that scan the perimeter for possible threats. All of the traditional perimeter systems require that security personnel must identify the source of alarms, either using imaging devices or by responding to the reported site in person and investigating the cause. For many large facilities, the local fauna provide a significant source of nuisance alarms that force the facility to expend significant resources to ensure adequate protection.
While infrared cameras provide a reasonable capability to enable security personnel to distinguish local fauna from human intruders, the effects of weather and foliage can severely degrade the captured image utility. Additionally, the costs associated with infrared imaging cameras often prohibit the use of the number of cameras that are needed to form images across the entire perimeter. A need therefore exists for a low cost alternative to infrared imaging for intruder classification that can work in substantially all weather conditions and in the presence of foliage.